1. Renal Replacement Therapies (RRT)
Renal Replacement Therapy (RRT) can be performed in specialized dialysis centers for treatment of chronic patients that have permanently lost kidney function and in hospitals for treatment of patients with a need for temporary replacement of renal function. Different modalities of Continuous Renal Replacement Therapy (CRRT) have been used to treat patients suffering from excess fluid overload and acute renal failure. In acute settings, CRRT has been performed using standard methods of hemodialysis and continuous arterio-venous hemofiltration (CAVH). More recently, continuous veno-venous hemofiltration (CVVH) has been used to reduce the complications associated with such issues as hemodynamic instability and need for arterial access. Regardless of the type of medical equipment used and the specific type of treatment performed, RRT requires establishing an extracorporeal blood circulation path that passes blood through a filtration device.
RRT performs two primary blood treatment functions: ultrafiltration (removal of water from blood plasma), and solute clearance (removal of different molecular weight substances from blood plasma). RRT involves the use of a filter in a blood circuit through which circulates extracorporeal blood temporarily withdrawn from a patient. The RRT filter, also called hemofilter or dialyzer, can be set up to perform either or both of these functions simultaneously, with or without fluid replacement, accounting for the various modes of renal replacement therapy. “Clearance” is a term that describes the removal of substances, both normal and waste product, from blood.
Ultrafiltration is the convective transfer of fluid out of a plasma compartment of a filter and through pores in the filter membrane. The pores of the filter membrane pass (filter) water, electrolytes and small and middle-sized molecules (up to 20,000 to 30,000 daltons) from the blood plasma. Large molecules, proteins blood cells and other large-sized plasma components (as well as a portion of the water and smaller components) do not pass through the filter membrane and remain in the plasma compartment of the blood circuit and are returned to the patient. The ultrafiltrate output (e.g., water extracted from the blood) from the filtration pores is similar to plasma, but without the plasma proteins or cellular components. Since the concentration of small solutes is the same in the ultrafiltrate as in the plasma, no clearance is obtained from the plasma, but fluid volume, e.g., water, is removed.
Dialysis is the diffusive transfer of small solutes out of a blood plasma compartment of a filter by diffusion across the filter membrane. This transfer occurs as a result of a concentration gradient, with diffusion occurring from the filter compartment with higher concentration (typically the blood compartment) to the filter compartment with lower concentration (typically the dialysate compartment). Since the concentration of solutes in the plasma decreases, clearance is obtained. Fluid may not be removed in dialysis. Ultrafiltration can be combined with dialysis to obtain both clearance and fluid removal from blood plasma.
Hemofiltration is the combination of ultrafiltration and fluid replacement in the treatment of blood. Typically, hemofiltration treats larger volumes of blood than is needed for fluid control alone. The replacement fluid added to blood during hemofiltration contains electrolytes, but not other small molecules. Since the net effect of replacing fluid without small solutes and ultrafiltration of fluid with small solutes results in net removal of small solutes, clearance is obtained during hemofiltration.
RRT devices typically use sets of disposable blood passage circuits (generally referred to as “disposables”) generally including tubing, filters, catheters, sensors and connectors that form a fluid circuit and are in direct contact with the blood and the fluid removed from the blood. These disposables can be assembled from components made by various manufacturers. Some more expensive disposables such as dialyzers can be used several times to treat the same patient. In some cases, disposables come assembled and the user need only mount the disposable blood passage on an instrument and pumping machine, and then prime the blood passage with sterile saline solution prior to its use. When the RRT device is ready for use, it is connected to the network of disposable and fluid filled tubes and electronic sensors that include the disposable blood passageway.
2. Limitations of User Interface of Existing Devices for RRT
Modern RRT devices are microprocessor controlled. The microprocessor operates pumps, reads sensors and communicates with the user via a user interface regarding the RRT treatment. In advanced RRT devices, the user interface has a graphics display that may be a touch screen or have an associated keypad. By interacting with a display and keys, the user interface enables a user to control the RRT device and monitor its operation.
There is a long felt need for RRT devices that are operator friendly and fault tolerant. Simplifying the device setup and operation is helpful to minimizing training and reducing operator error. Implementing rules in software that can guide the user through the setup while not overly restricting the operating envelope of the device may be applied to improve the safety for patients and enhance the market adoption of the RRT device.
U.S. Pat. No. 5,858,239 discloses a dialysis machine that has a graphics display where a user is assisted by simple pictograms. A user interface that makes use of graphical icons is disclosed in U.S. Pat. No. 5,620,608 for a dialysis machine. These icons help a user of a dialysis device navigate through a menu system. A graphics user interface for an aphaeresis blood processing apparatus using pictorials is disclosed in U.S. Pat. No. 5,653,887, which displays icons and a symbolic diagram of the apparatus with an arrow pointing towards an element (blood centrifuge) requiring user attention. A graphical user interface for an RRT device is also disclosed in U.S. Patent Application Publication No. 2002/151804.